Process for preparing allylidenphosphoranes

ABSTRACT

Allylidene phosphoranes are prepared by a new process comprising reacting dialkyl aluminum alkylidene amides or bis(N-dialkyl aluminum-imino)alkanes which are obtainable from saturated aliphatic nitriles or dinitriles and dialkyl aluminum hydrides with alkylidene phosphoranes R3CH PR34. The allylidene phosphoranes are useful as intermediate products in the synthesis of 1,3-dienes which include insect attracting substances and flavoring agents, and in the synthesis of 1,5-dienes such as squalene.

D United States Patent 1 1 3,919,325 Bogdanovic Nov. 11, 1975 PROCESS FOR PREPARING 3095.454 6/l963 Marco er al .6 260/6065 P ALLYLIDENPHOSPHORANES 3.241266 4/1966 Spcziule et a]v 260/6065 P 3.3040333 2/]967 Truscheil et 21!v 260/6065 P lnvemorl Borlslflv Bogdanovlc. h m 3.647.856 3/l972 Josey i. 260/6065 P (Ruhr). Gen'nany 1723.537 3/!973 Buddrus 260/6065 P [73] Assignee: Studiengesellschaft Kohle mbH,

Mulheim (Ruhr), Germany Primary Examz'nerArthur P. Dcmers [22] Filed: Feb. 26, 1973 Agent, or Firm-Burgess, Dinklage &

211 Appl. No.1 335,986

[57] ABSTRACT [30] Fore'gn Apphcanon Pnomy Data Allylidene phosphoranes are prepared by a new pro- Marl. 1 2 G rm ny n 2209685 cess comprising reacting dialkyl aluminum alkylidene amides 0r bis(N-dialkyl aluminum-imino)alkanes US 260/6065 8 A; 260/486 R; which are obtainable from saturated aliphatic nitriles 260/52 260/632 0/668 R; 60/677 or dinitriles and dialkyl aluminum hydrides with alkyli- 260/680 R dene phosphoranes R"CH=PR i The allylidene phos- [51] III. Cl. C07J 9/36 phoranes are useful as intermediate products in the [58] Fleld of Search 260/6065 P synthesis of l,3-dienes which include insect attracting substances and flavoring agents. and in the synthesis [56] R er fies C l of l,5-dienes such as squalene.

UNITED STATES PATENTS 2.912.467 l [/1959 Gerecke 260/6065 P 7 Claims N0 Drawmgs 1 2 PROCESS FOR PREPARING with alkylidene phosphoranes R CH=PR The reac- ALLYLIDENPHOSPHORANES tion proceeds according to the following equation:

The present invention relates to a process for the pro- 2 1 duction of allylidene phosphoranes 1) having the for- 1 "Ma /CHCH=NAIR1 R"CH=PR;, C=CH C=PR,,* H,NAlR- R R R2 3 (IV) in (eq C=CH-( =PR-j R/ wherein R and R are hydrogen or same or difierent alkyl or cycloalkyl groups; R is H or alkyl, R is aryl. The alkyl groups may, for example, contain from I to 20 carbon atoms. The cycloalkyl groups may, for example from 5 to 12 carbon atoms. Allylidene phospho- The conventional processes for producing allylidene ranes wherein R is H and wherein R is C -H can be phosphoranes involve reacting allyl halides with terpreferably produced by the present process. tiary phosphines to form the corresponding allyl phos- Suitable reaction media for carrying out the reaction phonium salts (equation 1 and thereafter reacting the according to equation 4 include aliphatic and aromatic latter with organo-metallic compounds, metal amides hydrocarbons, ethers, amines, nitriles, sulfoxides and or metal alcoholates to effect hydrogen halide cleavage 2 halohydrocarbons. The preferred reaction temperature q n ranges between 0 and C. However, the reaction R2 69 M23 9 R The economy of this process is largely dependent may be carried out at temperatures in a range from upon the availability of the particular allyl halides. 50 to +50C.

The higher allyl halides which are required especially Dialkyl aluminum alkylidene amides may be used in syntheses of natural products must be produced in both in pure form and in the form of their solutions obmany cases in expensive multi-stage syntheses. tained by reacting nitriles with dialkyl aluminum hylt has now been found that allylidene phosphoranes drides or trialkyl aluminum compounds in hydrocarhaving the general formulae (1), (II) or (III) bons for the reaction with, for example, triphenyl phosphine methylene. Triphenyl phosphine methylene both 2 3 in pure crystalline form (German Pat. No. l 003 730) l and in solution produced in situ may be reacted with /C=CH C=PR (I) dialkyl aluminum alkylidene amides.

R The allylidene phosphoranes (I) prepared according 2 2 to equation 4 may be isolated in pure form or reacted R R R R directly in solution with aldehydes or ketones to form E)J conjugated dienes. Particularly suitable for the crystala a lization of allylidene phosphoranes are ethers and pen- I I tane. The removal of dialkyl aluminum amides from the R'P=C CH=C (CH)" CH C=PRl (ml toluene or benzene solutions of allylidene phosphoranes may be effected by adding potassium amide. Di- 1 2 alkyl aluminum amides form low soluble complex salts wherein R and R are hydrogen or same or difierent w potassium amide. These salts have the Composi alkyl or cycloalkyl groups R3 is hylirogen or an alklfl tion R AlNH ZKNH and can be separated by filtra. group, and R is an aryl group which may be substition.

mted x is a value f 4 to 20 and y is 3 or be It is a particular advantage of the present process that produced substantially more advantageously, 1.e. withy id n (n of the type 1 alkyl, 2 R3 H 4 out the preceding production of allyl halides by react- (:H5 are formed preferentially, eg in a proportion of ing the dialkylaluminum alkylidene amides (IV) or to in the cis form bis(N-dialkyl aluminum-imino)alkanes obtainable 60 from saturated aliphatic nitriles or dinitriles and dialkyl aluminum hydrides 'strate the formation of the y1ide",

Allylidene phosphoranes are useful as intermediate products in the synthesis of 1,3-dienes according to G. Wittig (cf. Houben-Weyl-Muller, Methoden der organischen Chemie, 4th edition, Vol. W 16, p. 550). According to E. E. van Tamelen, the 1,5-dienes which are present in natural products, e.g. squalene can also be produced through allylidene phosphoranes (.1.Amer. Chem. Soc., 92 (1970) 2139).

Examples of 1,3-dienes which are commercially in demand and have become readily obtainable by the invention include the insect attracting substances hexadeca--trans,l2 cis-dien-l-ol (Bombykol; of. A. Butenandt et al, Liebigs Ann. Chem, 658 (1962)65, and tetradeca-3-trans,5-cis-dienoic acid (Megatom acid; cf. 1. O. Rodin, M. Leaffer, R. Siverstein, J. Org. Chem, 35 1970)3152) and flavoring substances such as nona- 1-trans,3-cis-dienoic acid ethyl ester (flavoring agent of Williams pear; cf. G. Ohloff, Nachr. Chem. Techn., 19, 447 (1971)).

All of the reactions described in the following examples are carried out in an argon or nitrogen atmosphere because of the sensitivity to air and humidity of the materials used.

EXAMPLE 1 To a solution of 242 g. (3.50 moles) of isobutyronitrile in 0.5 liters of pentane are added dropwise within 4 hours 483 g. (3.40 moles) of diisobutyl aluminum hydride in 0.5 liters of pentane at 10 to C. while stirring. After standing for 12 hours at room temperature, pentane is distilled off and diisobutyl aluminum isobutylidene amide is obtained by distillation under high vacuum (b.p., l05-l 10C./10 mm.Hg) in pure form as a compound which is crystalline at room temperature. Yield: 637 g. (89% of the theoretical yield).

To a suspension of 6.7 g. (24 mmoles) of triphenyl phosphine methylene in 50 ml. of pentane is added dropwise at room temperature a solution of 5.0 g. (24 mmoles) of diisobutyl aluminum isobutylidene amide in 30 ml. of pentane. After stirring for 2 hours, the initially yellow suspension turns dark red. it is stirred for further 12 hours, and the deep red crystalline precipitate formed after this time is collected on a frit, washed with pentane and thereafter dried under vacuum (0.1 to 0.2 mm. Hg) to give 6.4 g. (81% of the theory) oftriphenylphosphine-3-methyl-buten-2-y1idene which is identical with respect to the [R and l-l-NMR spectra with the compound prepared by the method of G. Wittig and H. Pommer (German Pat. No. 1,003,730).

EXAMPLE 2 To a solution of 27.3 g. (0.13 moles) of diisobutyl aluminum isobutylidene amide in 260 ml of toluene is added dropwise at room temperature within 2 hours a solution of 32.5 g. (0.12 moles) of triphenyl phosphine methylene in 200 ml. of toluene. The solution obtained is then allowed to stand for 12 hours at room temperature. There are obtained 475 ml of a dark red toluene solution of triphenyl phosphine-3-methyl-buten-(2)- ylidene and diisobutyl aluminum amide. To demon- 3.8 g. (35.8 moles) of benzaldehyde are added dropwise at 0C. to 100 ml of this solution thereby decolorizing the solution. The organoaluminum compound is decomposed by carefully adding 10 m1. of water and 100 ml of 2N H 50 at 0C.. The organic layer is separated and the aqueous layer is extracted with 30 ml of ether. The combined extracts are successively shaken with sodium bicarbonate and sodium bisulfite solutions and water and dried over sodium sulfate. Evaporation of the solvents (at 20C. and 12 mm. Hg) and distillation under high vacuum gives 1.80 g. (45% of the theory, based on triphenyl phosphine methylene) of 1-pheny1-4-methylpentadiene-( 1,3) which consists of 69.5% of the cis-isomer and 30.5% of the trans-isomer.

To separate diisobutyl aluminum amide, 5.5 g. (0,1 moles) of potassium amid are added to 200 ml of the above-mentioned toluene solution of triphenyl phosphine-3-methylbuten-(2)-y1idene and diisobutyl aluminum amide. In doing so, slight evolution of heat can be observed. The mixture is stirred for 12 hours whereupon the solution is separated from the precipitated diisobutyl aluminum amide-potassium amide complex by filtration through a G-3 frit.

The ylide solution which contains only traces of aluminum is mixed with benzaldehyde as described above. Processing in the manner described above gives l-phenyl-4-methylpentadiene-( 1,3) (63% cis and 37% trans) in a yield of 46% of the theory (based on triphenyl phosphine methylene).

. EXAMPLE 3 Analogously to Example 1, 213 g. (1.50 moles) of diisobutylaluminum hydride and 83 g. (1.51 moles) of propionitrile in 0.5 liters of pentane give 260 g. (88% of the theory) of diisobutyl aluminum propylidene amide which is a colorless liquid having a boiling point of 1 161 l9C./10" mm. Hg.

To a suspension of 13.5 g. (49 mmoles) of triphenyl phosphine methylene in 100 ml of ether is added dropwise at 20C. with stirring a solution of 10.0 g. (51 mmoles) of diisobutyl aluminum propylidene amide in 50 ml. of ether. The deep red solution is then allowed to stand for 2 hours at 20C. Thereafter the solution is allowed to stand for 2 days at 78C. The triphenyl phosphine crotylidene crystallized after this time is freed from solvent by means of an immersion frit, washed with 10 ml of ether at -78C., and dried under vacuum (0.2 to 0.3 mm. Hg). The yield of pure triphenyl phosphine crotylidene having a cis content of to (according to the H-NMR spectrum) is 45 to 50% of the theory.

EXAMPLE 4 Analogously to Example 1, 206 g. (1.45 moles) of diisobutyl aluminum hydride and g. (1.45 moles) of n-butyronitrile in 1 liter of pentane give 278 g. (91% of the theory) of diisobutyl aluminum butylidene amide which is a colorless liquid having a boiling point of to "C/l0 mm. Hg.

When following the procedure of Example 3 with diisobutyl aluminum butylidene amide and triphenyl phosphine methylene in ether and subsequently crystallizing at 78C., there is obtained triphenyl phosphine penten-2-ylidene (yield, 55% of the theory) which, according to the H-NMR spectrum. consists of 72% cisand 28% trans-tripheny1 phosphine penten-Z-ylidene.

EXAMPLE 5 Analogously to Example 1, 58.5 g. (0.41 moles) of diisobutyl aluminum hydride and 40.0 G. (0.41 moles) of n-capronitrile in 250 ml of pentane give 92.5 g (94% of the theory) of diisobutyl aluminum hexylidene amide which is obtained in the form of a slightly yellowish liquid having a boiling point of 130 to 139C] mm. Hg.

When following the procedure of Example 3 with diisobutyl aluminum hexylidene amide and triphenyl phosphine methylene in ether and subsequently crystallizing at 78C., triphenyl phosphine hepten-Z-ylidene having a cis-content of 87% (detennined by the Wittig reaction) is obtained in a yield of about 50% of the theory.

EXAMPLES 6 to 10 Analogously to Example 3, the following further triphenyl phosphine allylidenes can be prepared from diisobutyl aluminum alkylidene amides and triphenyl phosphine methylene:

To a suspension of 12 g. (42 mmoles) of triphenyl phosphine ethylidene in 90 ml of ether is added at room temperature a solution of 4.5 g. (21 mmoles) of diisobutyl aluminum isobutylidene amide in 90 ml ether and the mixture is allowed to stand at room temperature. After 15 days, one fourth of the resultant deep red solution is mixed with 1.8 ml of benzaldehyde thereby decolorizing the solution. Further treatment in the manner described in Example 2 gives a mixture of the stereoisomeric l-phenyl-2,4-dimethyll ,3 pentadienes (CH l C=CH-C-(CH )=CHC.,H,,. which demonstrates the formation of triphenyl phosphine allylidene EXAMPLE 12 To a solution of 14.2 g. (100 mmoles) of diisobutyl aluminum hydride in 0.4 liters of pentane are added dropwise at 10 to 15C. 6.8 g. (50 mmoles) of and gradual precipitation of the bisylide (Cs sJa |"l- CH=CH(CH,).CH=CHCH=P(C..H,),

from the solution in the form of a red precipitate. After stirring for 12 hours at 20C., the bisylide is collected on a G3 frit, washed with pentane and dried under vacuum (0.2 to 0.3 mm. Hg). Yield, 28 g. (85% of the theory).

EXAMPLE 1 3 By the procedure of Example 12, 8.2 g. (50 mmoles) of sebaconitrile [NC(CH ),,CN] are reacted with 14.2 g. 100 mmoles) of diisobutyl aluminum hydride in 0.4 liters of pentane and the resultant l, l0-bis( N-diisobutyl-aluminylimino)decane is reacted with 27.6 g. (100 mmoles) of triphenyl phosphine methylene in 0.1 liters of ether to give the bisylide (C.,H.)$P=CH-CH=CH(CH,)..CH=CH- u s]:1 which is purified by recrystallization in ether. Yield, to of the theory.

EXAMPLE 14 By the procedure of Example 12, 15.0 g. I00 mmoles) of azelaonitrile [NC(CH CN] are reacted with 28.4 g. (200 mmoles) of diisobutyl aluminum hydride in 0.4 liters of pentane and the resultant 1,9- bis(N-diisobutyl-aluminyl-imino)-nonane is reacted with 55 g. (200 mmoles) of triphenyl phosphine methylene in 0.1 liters of ether to give 0.5 liters of a deep red ether-pentane solution of the bisylide s):| H= H(CHz)sCH=CH- CH=P(C.,H5)- To demonstrate the formation of the bisylide, one half of this solution is mixed with 4.4 g. mmoles) of acetaldehyde. Processing as described in Example 2 gives a mixture of the stereoisomeric pentadeca-2,4,l l,l3- tetraenes.

EXAMPLE 15 To a suspension of 3.0 g. (75 mmoles) of tri(m-tolyl)- methyl phosphonium bromide in 25 ml of ether are added at 0C. 5 ml. of a 1.5N n-butyl lithium solution in hexane and thereafter at room temperature 1.5 g. (76 mmoles) of diisobutyl aluminum propylidene amide. To demonstrate the formation of the tri(m-tolyl)phosphine crotylidene, the deep red solution is mixed after 4 hours with 0.8 g. of benzaldehyde thereby decolorizing the solution. Processing as described in Example 2 gives a mixture of the stereoisomers of l-phenyl-penta- 1,3-diene.

EXAMPLE 16 To a solution of 28.4 g. (0.2 moles) of diisobutyl aluminum hydride in 600 ml. of pentane were added dropwise at 10 to +15C. with stirring within 30 minutes 10.8 g. (0.1 moles) of adipodinitrile [NC(CH CN]. Stirring is continued for 2 hours at 25C: and then a suspension of 55.2 g. (0.2 moles) of triphenyl phosphine methylene in 200 ml of ether is added to the viscous solution of the l,6-di( N-diisobutylaluminumimino)hexane whereafter the suspension is stirredfor l hours at C. The deep red bis-ylide (V) form the bis-ylide (VII). The compound (VII) conpreclprta ted after this time was recovered in pure form tained in the solution was characterized by the Wittig by filtration, washing with ether or pentane and drying reaction with acetaldehyde to form the cyclohexane under vacuum. Yield, 33.l g. (52.5% of the theory). derivative (VIII).

c n N CH=N al 2CHg=P(C-t s):! 2 Hall -2H,Nal

C I N CH=N al Plcfin r, Pwt tli 2CH,.CHO

P( |i s):r P(C s)a not intercept-able (Vll) The structure of the bis-ylide (V) was confirmed by its What is claimed is: H-NMR spectrum and by the Wittig reaction with acl. A process for preparing an allylidene phosphorane etaldehyde giving the cyclopentane derivative (VI). of the formula (I), (II) or (ill) (Ca )a u s):i

HUM): HQHSH ZCHSCHO EXAMPLE 17 R2 R3 Analogously to the above example 16, 14.2 g (0.1 \C=(:H LL=PRa4 m moles) of diisobutyl aluminum hydride were allowed to react with 6.1 g. (50 mmoles) of heptane dinitrile [NC(CH NC] in 200 ml of pentane and the resultant T Ti 2 solution of l,7-bis(N-diisobutyl aluminum imino)- ep- 4 4 tane was subsequently reacted with 27.6 g. (0.1 moles) H -CHC CHI)I C=CH-A"PR" of triphenyl phosphine methylene in I00 ml of ether to is reacted with CH =P( C H 5 triphenyl phosphine methylene 3. The process of claim 1, wherein a member selected from the group consisting of aliphatic and aromatic hydrocarbons, ethers, amines, nitriles, sulfoxides and halohydrocarbons is used as solvent.

4. The process of claim 1, wherein said reaction is carried out at a temperature within the range from 50C. to +50C.

5. The process of claim 4, wherein said reaction is carried out at a temperature within the range from 0C. to 20C.

6. The process of claim 1, wherein when preparing triphenyl phosphinallydene of the type R alkyl, R R H, R C l-l the cis-isomer is preferentially formed.

7. The process of claim 1, wherein a phosphorane of formula (11) or (111) is produced by reacting the corresponding bis(N-dialkyl aluminum-imino) alkane with triphenyl phosphine methylene CH P(C H 

1. A PROCESS FOR PREPARING AN ALLYLIDENE PHOSPHORANE OF THE FORMULA (1), (11) OR (111)
 2. The process of claim 1, wherein dialkyl aluminum alkylidene amide of the type
 3. The process of claim 1, wherein a member selected from the group consisting of aliphatic and aromatic hydrocarbons, ethers, amines, nitriles, sulfoxides and halohydrocarbons is useD as solvent.
 4. The process of claim 1, wherein said reaction is carried out at a temperature within the range from -50*C. to +50*C.
 5. The process of claim 4, wherein said reaction is carried out at a temperature within the range from 0*C. to 20*C.
 6. The process of claim 1, wherein when preparing triphenyl phosphinallydene of the type R1 alkyl, R2 R3 H, R4 C6H5, the cis-isomer
 7. The process of claim 1, wherein a phosphorane of formula (II) or (III) is produced by reacting the corresponding bis(N-dialkyl aluminum-imino) alkane with triphenyl phosphine methylene CH2 P(C6H5)3. 